In a vehicle manufacturing line, a vehicle is formed by assembling twenty to thirty thousand parts in various assembly lines and welding processes. In particular, a vehicle body frame in a monocoque construction generally consists of three parts, as shown in FIG. 1, namely: a floor assembly 10 that is composed of a front end 11, a center floor 12, and a rear floor 13, and supports a driving part, such as an engine, a vehicle shaft, and seats; a side assembly that is composed of left and right side panels 21 and 22, and supports left and right sides of a vehicle body frame; and a cowl and roof assembly that is composed of a cowl 31 and a roof 32, and supports an upper portion of a vehicle body frame.
Although ways for assembling such a vehicle body structure are slightly different among vehicle manufacturing companies, they are substantially similar. That is, in a conventional method for assembling a vehicle body, as shown in FIG. 2, the front end 11, the center floor 12, and a rear floor 13 are fixed to each other by tack welding in a floor assembly key-welding process S10, and a plurality of parts of the front end 11, the center floor 12, and the rear floor 13 are completely fixed to each other by spot welding in a floor assembly respot process S20 that is composed of five steps.
The five steps of the floor assembly respot process S20 are as follows. At step S21, connecting member parts of the front end 11, the center floor 12, and the rear floor 13 are additionally welded along a vertical direction. At step S22, connecting side parts of the front end 11, the center floor 12, and the rear floor 13 are welded. Then, at step S23, connecting panel parts of the front end 11, the center floor 12, and the rear floor 13 are welded. At step S24, a center tunnel slanting part of a connecting part of the front end 11, the center floor 12, and the rear floor 13 are welded. Lastly, at step S25, the front end 11, the center floor 12, and the rear floor 13 are finally welded and a special welding is performed.
After the floor assembly 10 is formed in the floor assembly respot process S20, an overall vehicle body frame is formed by temporarily assembling left and right side panels 21 and 22, the cowl 31, and the roof 32 in a vehicle body build-up key-welding process S30. Then, in the vehicle body respot process S40, a plurality of parts of the left and right side panels 21 and 22, the cowl 31, and the roof 32 that are temporarily assembled are completely fixed by spot welding.
The steps of the vehicle body respot process S20 are as follows. At step S41, side flange portions for mounting the floor assembly 10 and the left and right side panels 21 and 22 together are welded, and at step S42, mounting portions between the left and right side panels 21 and 22 and the roof 32 are welded along a vertical direction. At step S43, mounting portions between the floor assembly 10 and the left and right side panels 21 and 22 that are positioned inside a vehicle body, and at step S44, rear wheel portions of the left and right side panels 21 and 22 and the floor assembly 10, are specially welded. Finally, at step S45, the floor assembly 10 and rear lamp portions of the left and right side panels 21 and 22 are welded together, and the cowl 31 and a dash portion of the front end 11 are welded together.
In the conventional method of assembling a vehicle body, the front end 11 is assembled to the center floor 12 and the rear floor 13 to form the floor assembly 10 in the floor assembly key-welding process S10 and the floor assembly respot process S20, and then the floor assembly 10 including the front end 11 flows through the remaining processes. Accordingly, a pitch P1 of each process becomes long to accommodate practically the length of the vehicle, so that required workspace also increases. That is, assembling the front end 11 to the center floor 12 in an early stage of the vehicle body assembling is required only for welding matching portions of the left and right side panels 21 and 22 and the cowl 31 thereto, but in other processes the pre-assembled front end 11 only increases the pitch between processes.
In addition, recently, there is a tendency of making related parts as a module, and a radiator support panel that is assembled to the front end is generally supplied as a module by assembling various parts such as a front bumper, a headlamp, and a radiator cooling system. Because the radiator support panel module is assembled in a trim line, the structural strength of a front portion of the front end 11 is not sufficient. Particularly, after the front end is assembled, the vehicle body may undergo much shuttling between stations along an assembly line, so that significant deformations of the vehicle body may occur. Such deformations result in a deterioration of a quality of the vehicle body.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.